2. digestive system Flashcards
includes
Gastrointestinal tract (GI) accessory organs
GI tract
tube from mouth to anus
accessory organs
- teeth, tongue, salivary glands
- pancreas
- liver, gallbladder
digestive system processes
ingestion
digestion
absorption
defecation
ingestion
food into oral cavity
digestion
- large molecules broken down into smaller molecules
* 2 types: mechanical and chemical
mechanical digestion
motility
eg. chewing
chemical
enzymes and acid secretions
absoroption
end products of digestion enter blood or lymph
defecation
elimination of waste and undigested material
GI tract histology
4 basic layers : mucosa submucosa muscularis externa serosa (or adventitia) enteric nervous system
mucosa
3 layers:
- epithelium with numerous goblet cells
- lamina propria=areolar CT
- muscularis mucosa
epithelium with numerous goblet cells
-stratified squamous: mouth, pharynx, esophagus anal canal
lamina propria
areolar CT
-contains blood, lymph vessels , lymph nodules/tissues (immune)
muscularis mucosa
smooth muscle-allows movement of mucosa
submucosa
areolar CT
contains : blood and lymphatic vessels, submucosal nerve plexus
muscularis externa
- smooth muscle
- inner circular layer
- outer longitudinal layer
- myenteric nerve plexus b/w layers
- contractions cause motility (mixing and movement)
serosa
or adventitia
-cavity=lumen
enteric nervous system
- nervous system of GI tract
- myenteric plexus
- submucous plexus
myenteric plexus
controls muscularis externa
submucous plexus
controls activity of mucosal glands and muscle
structures:
oral cavity salivary glands dentition (teeth) oropharynx and laryngopharynx esophagus stomach small intestine small intestinal accessory organs large intestine
oral cavity includes
lips
cheeks
palate
tongue
palate parts
hard palate
soft
hard palate
-2 maxillae and 2 palatine bones
soft palate
posterior to hard palate
skeletal muscle
posterior projection = uvula
rises to close the nasopharynx when swallowing
tongue
attached to hyoid bone
skeletal muscle
projections of mucosa=papillae (taste buds)
salivary glands 3 pairs:
parotid
submandibular
sublingual
also contains saliva
parotid
- inferior and anterior to ears
- mumps=inflammations of 1 of both parotids
submandibular
floor of mouth
sublingual
below tongue on floor of mouth
saliva
- 5% H2O
0. %% solutes (eg.enzymes)
dentition (teeth)
-in maxillae and mandible
go to page 3
child dentition
primary dentition-deciduous (“baby”) teeth
has 20 teeth
adult dentition
secondary dentition-permanent teeth
has 32 teeth
tooth struture
crown root neck periodontal ligaments root canal extend to pulp cavity
crown
above the gum
dentin=majority of tooth
enamel overlay=acellular, highly calcified-hard!
root
dentin with cementum overlay
dentin, enamel and cementum
similar to bone, but avascular
neck
enamel and cementum boundary (gums)
periodontal ligaments
attach root to bones
root canal extends to pulp cavity
contains CT, blood/lymph vessels, and nerves
oropharynx and laryngopharynx
only muscularis externa (skeletal muscle) and mucosa (stratified squamous epithelium)
esophagus
- posterior to trachea
- passes through diaphragm to the abdominal cavity
- all 4 histological layers in GI tract from this point on
exceptions in esophagus
- muscularis externa
- has adventitia in mediastinum
muscularis externa
- upper 1/3-skeletal muscle
- middle 1/3-skeletal and smooth muscle (transition zone)
- lower 1/3-smooth muscle
has adventitia in mediastinum
-outermost layer
=fibrous CT (no epithelium)
stomach has 4 regions
- cardiac region
- fundus
- body
- pyloric region
cardiac region
cardia
attached to esophagus
fundus
above esophageal entrance
pyloric region
pylorus
has pyloric sphincter
stomach
- greater and less curvatures
- converts food into chime (food and gastric juice)
- stomach mucosa
stomach mucosa
- invaginations of epithelium forms gastric glands (exocrine)
- secrete gastric juice to lumen
gastric glands contain:
chief cells
parietal cells
goblet cells
G cells
chief cells
secrete pepsinogen and gastric lipase (enzymes)
parietal cells
secrete HCl and intrinsic factor (for vit B12 abs in ileum)
goblet cells
mucus ( surface epithelium also contains many goblet cells)
G cells
enteroendocrine cells
-secrete gastrin (hormone; to blood)
rugae
folds of the mucosa and submucosa due to contraction of muscularis mucosa
-allow expansion without tearing mucosa
muscularis externa
-function = churning 3 layers: inner oblique middle circular outer longitudinal
small intestine
pyloric sphincter to ileocaecal valve
small intestine 3 segments
duodenum
jejunum
ileum
duodenum
first fold (short)- retroperitoneal -extra glands here secrete alkaline mucus to protect against stomach acid
jejunum
middle section
ileium
has groups of lymph nodules=peyer’s patches
-prevent infection of small intestine and bacteria from entering blood
segments specialized to increase absorption surface area in the small intestine
plicae circulares
villi
microvilli
plicae circulares
submucosa thrown into folds
villi
projections of mucosa into lumen
contains:
blood capillaries
lacteals (lymph capillaries that absorb eg. fats )
microvilli
brush border on enterocytes (simple columnar)
-extend into lumen
-within epithelium, separate enteroendocrine cells secrete the hormones:
secretin
cholecystokinin
small intestinal accessory organs
pancreas
liver
gallbladder
pancreas
retroperitoneal
parts: head, body, tail
contains: exocrine portion and endocrine portion
exocrine portion
- acinar cells/acini (most of pancreas)
2. duct cells
acinar cells/acini (most of pancreas)
secrete digestive enzymes ( into ducts )
duct cells
secrete alkaline fluid to neutralize stomach acid
->digestive enzymes and alkaline fluid =pancreatic juice
endocrine portion
=islets of langerhans (amid acini)
-secrete hormones: insulin and glucagon to regulate blood sugar
liver
- 4 lobes (right, left, caudate, quadrate)
- cells=hepatocytes
- filters material from GI tract (nutrients, toxins etc) before going to rest of body produce bile
- produces bile-for fat digestion
gallbladder
muscular sac on surface of liver rugae, no submucosa stores, concentrates bile b/w meals -> enzymes, alkaline fluid and bile enter duodenum by series of ducts page 7
large intestine
- ileocaecal valve to anus
- appendix
- colon
- rectum
- anus
colon parts
- ascending (right side)
- hepatic flexure
- transverse
- splenic flexure
- descending (left side)
- sigmoid
colon
- muscularis externa longitudinal layer incomplete = taeniae coli
- contraction forms pouches = haustra
- epiploic appendages = fat- filled pouches
- function unknown
rectum
no taeniae coli
-anal canal=last 3 cm
anus
-2 anal sphincters: internal (smooth muscle) and external (skeletal muscle-voluntary control)
lymphatic system of intestines contains
immune function
digestive function
immune function
- lymph nodules in mucosa throughout small and large intestines
- peyer’s patches in ileum
- prevents infection of small intestine and prevent bacteria from entering blood
digestive function
lymph vessels
-most absorbed fats from small intestine enter lacteals (some into blood)
lacteals ->lymph collecting vessels->cisterna chyli-> thoracic duct->left subclavian vein
lower GI tract blood circulation
page 9
portal system
portal system
blood vessels b/w 2 capillary beds 9but blood doesn’t pass through the heart b/w them)
peritoneum
serous membrane serosa b/w organs mesentery retroperitoneal peritonitis (page 10 diagram)
serous membrane
- visceral peritoneum (against organ wall)
- parietal peritoneum (against abdominal cavity wall)
- peritoneal cavity = filled with serous fluid
serosa b/w organs
sheet of w fused visceral peritoneum layers
-contains blood/lymph vessels and nerves
-forms folds in some areas=omenta:
greater and lesser omentum
greater omentum
- fatty apron
- covers transverse colon and small intestine
- contains fat-protection, insulation, energy reserve
lesser omentum
suspends stomach from liver
mesentery
- suspends small intestine from cavity wall
- double layer of parietal peritoneum
retroperitoneal
- an organ behind peritoneum
- peritoneum lines only one side
- anterior = parietal peritoneum
- posterior = CT (adventitia)
peritonitis
- inflammation of the peritoneum
- due to:burst appendix, wounds etc.
